The present invention relates to a belt pulley arrangement.
Belt pulley arrangements are used, for example, in belt drives of motor vehicles. An auxiliary unit driven by a belt drive can be, for example, a generator, an electric machine that can be operated as a generator or as an electric motor, an air-conditioning system compressor, or a pump, each of which can be driven by the crankshaft of an internal combustion engine via a drive belt. While internal combustion engines are running, rotational imbalances or rotational oscillations occur in the crankshaft, as well as drivetrain oscillations during shifting processes of vehicle transmissions, for example, during start-stop processes. To prevent these rotational oscillations from being transmitted disadvantageously to the drive shafts of the auxiliary units, it is known to equip belt pulley arrangements with decoupling means that make sure that rotational oscillations are not transmitted at all or only to a damped degree to the driveshaft of the auxiliary units. The decoupling means are usually free-running devices that enable torque to be transmitted from the belt pulley to the driveshaft of the auxiliary unit, but prevent torque transmission in the opposite load direction.
DE 10 2009 052 611 A1 discloses a belt pulley arrangement with a hub that can be fastened to a driveshaft, a belt pulley supported so that it can rotate on the hub, as well as a bracket-less torsion spring. The torsion spring extends axially between the hub and belt pulley and is arranged radially between the hub and belt pulley. By means of the torsion spring, a torque transmission between the belt pulley and hub is made possible. For this purpose, the torsion spring is arranged with its one end against the hub and with its other end against the belt pulley. The belt pulley arrangement also has a free-running device that consists of a looped flat spiral spring arranged radially between the hub and belt pulley as well as coaxial to the torsion spring. The torsion spring has a greater winding diameter than the looped flat spiral spring. The looped flat spiral spring is arranged on the radial inside and faces the hub. The torsion spring is arranged on the radial outside and faces the belt pulley.
WO 2014/007906 A1 describes a belt pulley arrangement with a belt pulley supported on a shaft, a torsion spring, and a looped flat spiral spring that is arranged radially within the torsion spring and wound around the shaft. If a predetermined torque is exceeded, an overload function is activated. For this purpose, the belt pulley has an engagement surface that can be brought into engagement with one end of the looped flat spiral spring, wherein the looped flat spiral spring is angled away from the shaft and the friction engagement of the looped flat spiral spring with the shaft is reduced. If the belt pulley rotates in the opposite direction, the torque of the belt pulley can no longer be transmitted, because the looped flat spiral spring is actuated in the opening direction. In this situation there is the risk that the torsion spring is not driven and can become jammed axially in the interior space.
EP 1 692 409 B1 includes a decoupler arrangement with a hub that is attached rigidly on a shaft and extends axially between a first and a second end. A belt pulley is fastened to the hub so that it can rotate. A carrier that has a first and a second side, as well as a retaining bump projecting from one of the sides, is mounted around the first end of the hub. Between the hub and carrier extends a torsion spring for transmitting torque between the hub and carrier. On the first end of the hub, a thrust plate is attached rigidly that has a slot for holding the retaining bump. The retaining bump can be moved in the slot, in order to limit the rotation of the carrier and the thrust plate relative to each other and simultaneously to prevent a selective rotational movement of the torsion spring relative to the hub and to the carrier. The decoupler arrangement can be equipped with a free-running coupling device arranged between the torsion spring and belt pulley in the form of a looped flat spiral spring.